In addition to being scientifically exciting, commercially important, and environmentally essential, temperate forests have also become a key diplomatic item in international climate negotiations as potential sinks for carbon. This review presents the methods used to estimate carbon sequestration, identifies the constraints and opportunities for carbon sequestration in temperate forests, addresses the issues raised by the monitoring of carbon sequestration, and analyzes uncertainties pertaining to the sequestration of carbon by temperate forests. This review serves a dual purpose: It aims at informing policy makers about carbon sequestration in temperate forests and at making forest ecologists, biogeochemists, and atmospheric scientists aware of the structure of an international agreement to reduce CO2 and other greenhouse gas emissions and some of the real, still answered scientific questions that it poses.